Network configuration / following control mode switching method and device of wind turbine generator

Abstract

The invention provides a network construction / following control mode switching method and device for a wind turbine generator, and the method comprises the steps: receiving a grid-connected control instruction, and carrying out the pre-synchronization control of the voltage, frequency and phase at two ends of a grid-connected point; wherein a grid-connected inverter of the wind turbine generator is in a network construction control mode before the grid-connected control instruction is received; carrying out pre-synchronization control on direct-axis current and quadrature-axis current on a grid-connected inverter of the wind turbine generator; if it is judged that the current value of the direct axis and the feedback current value of the direct axis meet the first switching trigger condition and the current value of the quadrature axis and the feedback current value of the quadrature axis meet the second switching trigger condition, control mode switching is conducted. The device is used for executing the method. According to the network configuration / following control mode switching method and device of the wind turbine generator, stable operation of the wind turbine generator is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a method and device for switching a wind turbine generator set's control mode between a grid-following control mode and a grid-following control mode. Background Art

[0002] Grid-connected wind turbines can actively provide the necessary voltage and frequency support for the power grid. They can also operate independently in an unstable or isolated grid state, demonstrating strong adaptability and stability.

[0003] Grid-type wind turbines can still maintain stable output in a weak grid environment, providing strong support for the grid. Compared with grid-following devices, grid-type converters have independent networking, frequency / voltage support, black start and other additional functions. In microgrid systems, they often face the need to switch the grid-following control strategy in the grid-connected mode. The switching process usually produces a large impact that affects the stable operation of the system. Therefore, how to propose a switching method for the grid-following control strategy, reduce the grid-connected impact, and improve the stability during the switching process has become an important issue that needs to be solved in this field. Summary of the invention

[0004] In view of the problems in the prior art, an embodiment of the present invention provides a method and device for switching the configuration / grid-following control mode of a wind turbine generator set, which can at least partially solve the problems in the prior art.

[0005] In a first aspect, the present invention provides a method for switching a wind turbine generator set between a grid-following control mode and a grid-following control mode, comprising:

[0006] Receive a grid-connected control instruction, and perform pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine generator set is in a grid-connected control mode;

[0007] Performing pre-synchronization control of the orthogonal axis current on the grid-connected inverter of the wind turbine generator set;

[0008] If it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition, the control mode is switched.

[0009] In a second aspect, the present invention provides a device for switching a wind turbine generator set's control mode from one to another, including:

[0010] A receiving module, used for receiving a grid-connected control instruction and performing pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine generator set is in a grid-connected control mode;

[0011] A control module, used for performing pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine generator set;

[0012] The switching module is used to switch the control mode after determining that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition.

[0013] In a third aspect, the present invention provides a computer device, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the program to implement the method for switching the wind turbine generator set configuration / grid-following control mode as described in any of the above embodiments.

[0014] In a fourth aspect, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program / instruction, which, when executed by a processor, implements the method for switching the wind turbine configuration / grid-following control mode as described in any of the above embodiments.

[0015] In a fifth aspect, the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the method for switching the wind turbine configuration / grid-following control mode as described in any of the above embodiments.

[0016] The method and device for switching the structure / grid-following control mode of a wind turbine set provided in an embodiment of the present invention receive a grid-connected control instruction and perform pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; perform pre-synchronization control of the direct-axis and cross-axis currents of the grid-connected inverter of the wind turbine set; if it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the cross-axis current value and the cross-axis feedback current value meet the second switching trigger condition, then control mode switching is performed to achieve smooth switching of the control mode, thereby ensuring stable operation of the wind turbine set. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0018] Figure 1 It is a flow chart of a method for switching between a wind turbine generator set configuration / grid-following control mode provided by the first embodiment of the present invention.

[0019] Figure 2 It is a flow chart of a method for switching the wind turbine generator set configuration / grid-following control mode provided by the second embodiment of the present invention.

[0020] Figure 3 It is a topological diagram of a simulation model of a direct-drive wind turbine grid-connected system provided in the third embodiment of the present invention.

[0021] Figure 4 A schematic diagram of smooth switching control based on self-closed loop regulation of dq axis reference current provided in the fourth embodiment of the present invention.

[0022] Figure 5 This is a topological diagram of the improved control mode smooth switching flow chart provided in the fifth embodiment of the present invention.

[0023] Figure 6 This is a diagram of simulation results for comparing d-axis reference control current under different schemes provided in the sixth embodiment of the present invention.

[0024] Figure 7 This is a simulation result diagram comparing the changes in inverter output power under different schemes provided in the seventh embodiment of the present invention.

[0025] Figure 8 This is a diagram of simulation results comparing system frequency changes under different schemes provided in the eighth embodiment of the present invention.

[0026] Fig. 9 It is a structural schematic diagram of a wind turbine generator set configuration / grid-following control mode switching device provided in the ninth embodiment of the present invention.

[0027] Fig.10 It is a structural schematic diagram of a wind turbine generator set configuration / grid-following control mode switching device provided in the tenth embodiment of the present invention.

[0028] Fig.11 It is a structural schematic diagram of a wind turbine generator set configuration / grid-following control mode switching device provided in the eleventh embodiment of the present invention.

[0029] Fig.12 It is a schematic diagram of the physical structure of a computer device provided in the twelfth embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily. The acquisition, storage, use, and processing of data in the technical scheme in this application comply with the relevant provisions of laws and regulations. The user information in the embodiments of the present application is obtained through legal and compliant channels, and the acquisition, storage, use, and processing of user information are authorized and agreed by the customer.

[0031] In order to facilitate understanding of the technical solution provided by this application, the relevant contents of the technical solution of this application are first explained below.

[0032] In a microgrid system, there is often a need to switch between the grid-connected control strategy and the root grid control strategy in the grid-connected mode. The switching process usually generates a large impact that affects the stable operation of the system. In order to enable the grid-connected wind turbine to have smooth switching capabilities, it is necessary to improve the current switching method to achieve smooth switching between the grid-connected control mode and the root grid control mode, and ensure the stable operation of the grid-connected wind turbine. Therefore, an embodiment of the present invention provides a switching method for a control mode based on self-closed-loop regulation of the dq-axis current. By designing a current switcher with self-closed-loop regulation, the sudden change of the dq-axis reference control current when the control mode is switched from the grid-connected control mode to the root grid control mode is mitigated, thereby achieving smooth switching of the control mode and ensuring the operating stability of the inverter during the switching process.

[0033] Figure 1 FIG. 1 is a flow chart of a method for switching a wind turbine generator set configuration / grid-following control mode according to a first embodiment of the present invention. Figure 1 As shown, the method for switching the wind turbine generator set configuration / grid-following control mode provided by the embodiment of the present invention includes:

[0034] S101, receiving a grid-connected control instruction, and performing pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine generator set is in a grid-connected control mode;

[0035] Specifically, the grid-connected inverter of the wind turbine is in the grid-connected control mode. After receiving the grid-connected control instruction, the voltage, amplitude and frequency at both ends of the grid-connected point will be pre-synchronized so that the voltage, frequency and phase at both ends of the grid-connected point can meet the grid-connected conditions. The pre-synchronization control of voltage, amplitude and frequency can be carried out in the existing technology, which will not be described in detail here.

[0036] S102, performing pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine generator set;

[0037] Specifically, when the grid-connected inverter is running, only one control mode will be in a normal state, and the other control mode cannot form a closed loop. When the grid-connected inverter is in the grid-building control mode, the orthogonal axis (hereinafter referred to as dq axis) current value output in the non-operating state is not equal to the dq axis current value in the operating state of the current grid-building control mode, which is bound to lead to a sudden change in the instantaneous current during switching, causing a grid-connected shock. Therefore, the present application performs pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine group to reduce the sudden change in the dq axis current value, so as to achieve a smooth transition when the grid-building control mode is switched to the grid-following control mode.

[0038] S103: If it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition, switch the control mode.

[0039] Specifically, it is determined whether the current value of the direct axis (hereinafter referred to as d-axis) and the feedback current value of the d-axis meet the first switching trigger condition, and it is determined whether the current value of the quadrature axis (hereinafter referred to as q-axis) and the feedback current value of the q-axis meet the second switching trigger condition. If the current value of the d-axis and the feedback current value of the d-axis meet the first switching trigger condition, and the current value of the q-axis and the feedback current value of the q-axis meet the second switching trigger condition, then the control mode is switched, that is, the grid-connected inverter of the wind turbine group is switched from the grid-building control mode to the grid-following control mode.

[0040] The method for switching the control mode of a wind turbine generator set provided in an embodiment of the present invention receives a grid-connected control instruction and performs pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; performs pre-synchronization control of the direct-axis and cross-axis currents of the grid-connected inverter of the wind turbine generator set; if it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the cross-axis current value and the cross-axis feedback current value meet the second switching trigger condition, then the control mode is switched to achieve smooth switching of the control mode, thereby ensuring the stable operation of the wind turbine generator set.

[0041] Figure 2 FIG. 1 is a flow chart of a method for switching a wind turbine generator set configuration / grid-following control mode according to a second embodiment of the present invention. Figure 2 As shown, based on the above embodiments, further, the pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine generator set includes:

[0042] S201, performing a first-level proportional-integral adjustment based on a first difference between the direct-axis current value and the direct-axis feedback current value to generate an active reference; performing a first-level proportional-integral adjustment based on a second difference between the quadrature-axis current value and the quadrature-axis feedback current value to generate a reactive reference;

[0043] Specifically, the difference between the current value of the d-axis and the feedback current value of the d-axis (i.e., the first difference) is adjusted by the first level proportional-integral (PI) to generate an active reference. The difference between the current value of the q-axis and the feedback current value of the q-axis (i.e., the second difference) is adjusted by the first level PI to generate a reactive reference.

[0044] S202. Perform a second-level proportional-integral adjustment based on the third difference between the active reference amount and the active voltage to update the feedback current value of the direct axis; perform a second-level proportional-integral adjustment based on the fourth difference between the reactive reference amount and the reactive voltage to update the feedback current value of the quadrature axis.

[0045] Specifically, the difference between the active reference and the active voltage is subjected to a second-level PI adjustment to obtain a new direct-axis feedback current value, and the original direct-axis feedback current value is updated. The difference between the reactive reference and the reactive voltage is subjected to a second-level PI adjustment to obtain a new quadrature-axis feedback current value, and the original quadrature-axis feedback current value is updated. Among them, the parameters such as the proportional coefficient and the integral coefficient adopted by the first-level proportional-integral adjustment and the second-level proportional-integral adjustment are set according to actual needs, and are not limited in the embodiment of the present invention.

[0046] Among them, the active voltage and reactive voltage can be obtained by collecting the voltage of the DC bus between the equivalent power source composed of the wind turbine and the machine-side converter and the grid-connected inverter.

[0047] On the basis of the above embodiments, further, the method for switching the wind turbine generator set control mode between the grid control mode and the grid control mode provided by the embodiment of the present invention further includes:

[0048] If it is determined that the direct-axis current value and the direct-axis feedback current value do not satisfy the first switching trigger condition or the quadrature-axis current value and the quadrature-axis feedback current value do not satisfy the second switching trigger condition, the pre-synchronization control of the direct-axis and quadrature-axis currents of the grid-connected inverter of the wind turbine group continues.

[0049] Specifically, if the current value of the d-axis and the feedback current value of the d-axis do not meet the first switching trigger condition, or the current value of the q-axis and the feedback current value of the q-axis do not meet the second switching trigger condition, it means that smooth switching of the control mode cannot be achieved at present, then the pre-synchronization control of the DC-axis current of the grid-connected inverter of the wind turbine group will continue until the current value of the DC-axis and the feedback current value of the DC-axis meet the first switching trigger condition and the current value of the DC-axis and the feedback current value of the DC-axis meet the second switching trigger condition, and the control mode can be switched.

[0050] On the basis of the above embodiments, further, the first switching trigger condition includes that an absolute value of a first difference between the current value of the direct axis and the feedback current value of the direct axis is less than or equal to a first threshold;

[0051] The second switching triggering condition includes that an absolute value of a second difference between the quadrature-axis current value and the quadrature-axis feedback current value is less than or equal to a second threshold.

[0052] Specifically, the absolute value of the first difference between the d-axis current value and the d-axis feedback current value may be calculated, and the absolute value of the first difference may be compared with a first threshold to determine whether the absolute value of the first difference is less than or equal to the first threshold.

[0053] The absolute value of the second difference between the q-axis current value and the q-axis feedback current value may be calculated, and the absolute value of the second difference may be compared with a second threshold value to determine whether the absolute value of the second difference is less than or equal to the second threshold value.

[0054] If the absolute value of the first difference is less than or equal to the first threshold and the absolute value of the second difference is less than or equal to the second threshold, the control mode will be switched; if the absolute value of the first difference is greater than the first threshold, or the absolute value of the second difference is greater than the second threshold, the control mode will not be switched. The first threshold and the second threshold are set according to actual needs and are not limited in the embodiment of the present invention.

[0055] like Figure 3 As shown, the direct-drive wind turbine grid-connected system includes a direct-drive wind turbine, a back-to-back converter and a microgrid. The direct-drive wind turbine includes a permanent magnet synchronous generator set, and the back-to-back converter includes a machine-side converter and a grid-connected inverter (also called a grid-side converter). The permanent magnet synchronous generator set is connected to the AC bus through the back-to-back converter, and the AC load is directly connected to the AC bus. The direct-drive wind turbine is used to generate power, and the machine-side converter adopts a fixed DC voltage control; the grid-connected inverter adopts a grid-type control mode based on virtual synchronous control to provide voltage and frequency support. In the grid-side control, MPPT and secondary frequency modulation control are used to generate active power reference values, and active frequency control and AC voltage control are used to generate reference amplitudes and phases of AC voltage. The output power of the direct-drive wind turbine flows out through the back-to-back converter, and is collected to the AC bus together with the power output of the microgrid, and finally flows to the AC load through the AC bus. The grid-connected inverter adopts virtual synchronous machine control technology and uses a self-closed-loop regulated current switch to reduce the impact on the system, thereby achieving smooth switching of the system's control mode.

[0056] like Figure 4 As shown, the present invention proposes a principle of smooth switching between a direct-drive wind turbine and a grid-building control strategy based on self-closed-loop regulation of the dq-axis reference current. The system monitors and identifies the currently activated control mode, and ensures that no control conflict is introduced during the switching process. In the preparation stage of the control mode switching, the system pays attention to the control mode in the non-operating state, which may produce dq-axis current values ​​that are inconsistent with the operating state when a closed loop is not formed. This inconsistency may cause a sudden change in current at the moment of switching, thereby affecting the stability of the system. In order to solve this problem, before switching, the grid-connected inverter is in the grid-building control mode (corresponding to the switch point S1), and the d-axis current value I dref As I * drefOutput to the current loop, q-axis current value I qref As I * qdref Output to the current loop. At the same time, the closed-loop control part pre-synchronizes the dq axis current through a double-layer PI control link to obtain the feedback current value I of the d axis after closed-loop adjustment. Idref and the q-axis feedback current value I Iqref Specifically, the d-axis current value I dref and the d-axis feedback current value I Idref After the difference is adjusted by the first layer PI, the active reference quantity P is generated. Iref ;q-axis current value I qref and the q-axis feedback current value I Iqref After the difference is adjusted by the first layer PI, the reactive reference quantity U is generated. Iref Active reference quantity P Iref and active voltage P e After the difference is adjusted by the second layer PI, the feedback current value I of the d-axis is obtained. Idref ; Reactive reference quantity U Iref and reactive voltage U dc After the difference is adjusted by the second layer PI, the feedback current value I of the q axis is obtained. Iqref .

[0057] Taking the control of d-axis current as an example, the mathematical model of d-axis current closed-loop control is shown below.

[0058]

[0059] Among them, k dpII Indicates the second-level PI proportional coefficient of the active link; k diII Indicates the second-level PI integral coefficient of the active link; 1 / s d represents the integral link; k dpI Indicates the first-level PI proportional coefficient of the active link; k diI It indicates the first-level PI integral coefficient of the active link.

[0060] For I in formula (1) dref with I Idref By disassembling and separating them respectively, we can get the following expressions:

[0061]

[0062] In the steady-state stage of the closed-loop control link, P e Considered as a constant, the following equation holds.

[0063]

[0064] It can be seen that after controlling the d-axis current pre-synchronization, Idref =I Idref =I * dref .

[0065] The closed-loop control of the q-axis current is similar to that of the d-axis current. The mathematical model of the d-axis current closed-loop control is shown below.

[0066]

[0067] Among them, k qpII Indicates the second-layer PI proportional coefficient of the reactive link; k qiII Indicates the second-level PI integral coefficient of the reactive link; 1 / s q represents the integral link; k qpI Indicates the first-layer PI proportional coefficient of the reactive link; k qiI It indicates the first-level PI integral coefficient of the reactive link.

[0068] After controlling the q-axis current pre-synchronization, I qref =I Iqref =I * qref The specific implementation process is similar to that of the d-axis and will not be described in detail here.

[0069] Since there are certain errors in actual control, the switching trigger conditions can be set as:

[0070]

[0071] When equation (5) holds true, the control mode can be switched.

[0072] According to formula (5), the d-axis current value I of the input current loop is calculated dref The feedback current value I of the d-axis generated by the closed-loop control link Idref The absolute value of the difference A1 is calculated, and the q-axis current value I of the input current loop is calculated. qref The feedback current value I of the q-axis generated by the closed-loop control link Iqref If A1 is less than or equal to T1, and A2 is less than or equal to T2, it means that the inrush current caused by the switching of the control mode is small, and the control mode switching command can be executed. Figure 5 The switch point S1 in the circuit is switched to the switch point S2, so that the control mode is switched from the network building control mode to the network following control mode.

[0073] If A1 is greater than T1, or A2 is greater than T2, it means that the impact current caused by the switching of the control mode is large, and the pre-synchronization control of the orthogonal axis current will continue until A1 is less than or equal to T1 and A2 is less than or equal to T2, and the switching of the control mode is completed.

[0074] like Figure 5 As shown, after the grid-type VSG control, the output reference electromotive force E abc , electromotive force E abc Output d-axis current value I through voltage loop dref and q-axis current value I qref Then, the current switch is controlled to output I * dref and I * qdref To the current loop, after the control of the current loop, the control voltage U of the grid-connected inverter is finally output. * abc .

[0075] like Figure 6 As shown in Figure 2, during the 0s to 20s period, the inverter is in the grid control mode. Figure 6 It can be seen that the d-axis current I under network control d At the 6th second, it can be stabilized at about 11.5kA. Figure 6 As shown by the red line in the figure, in the current accumulation synchronization stage, the reference current of the grid control can follow the reference current of the grid control and finally lock the synchronization. Figure 6 The reference current open loop control ( Figure 6 As shown by the black line in the figure, there is a certain allowable error between the actual power output by the inverter and the reference power, and the error always exists after the system stabilizes. The error is accumulated and superimposed through the PI integral link, so the output current value presents an uncontrolled straight-line rise after the system stabilizes. At the 20th second, its value is about 12.8kA. As the time in the system operation mode increases, the deviation of the control current reference becomes larger, and the impact on the system becomes greater. This verifies the effectiveness of the reference control current closed-loop strategy proposed in this application.

[0076] like Figure 7 As shown, the control mode direct switching strategy has greater fluctuations than the strategy proposed in this article (i.e., the wind turbine configuration / grid-following control mode switching method of this application). Of the two, the maximum power fluctuation difference of the former is 13.4MW-11.3MW=2.1MW, while the maximum power fluctuation difference of the latter is 12.3MW-11.8MW=0.5MW. Similarly to the above, this is because the inverter under grid-type control behaves actively, and similarly to the above, there is a certain error in the key parameters when the control strategy is switched, and the inverter needs to re-establish balance with the system. During the period of establishing balance, the system is subjected to a certain impact. The strategy proposed in this article can make the switching process smoother and less impactful by controlling the current self-closed loop method.

[0077] like Figure 8As shown, the strategy proposed in the present invention reduces the impact of the network switching on the system frequency, and the frequency fluctuation is less than 0.1Hz; the control mode direct switching strategy has a slightly larger fluctuation.

[0078] Fig. 9 is a schematic diagram of the structure of a wind turbine generator set configuration / grid-following control mode switching device provided by a ninth embodiment of the present invention, such as Fig. 9 As shown, the wind turbine generator set configuration / grid-following control mode switching device provided by the embodiment of the present invention includes a receiving module 901, a control module 902 and a switching module 903, wherein:

[0079] The receiving module 901 is used to receive the grid-connected control instruction and perform pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine is in the grid-connected control mode; the control module 902 is used to perform pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine; the switching module 903 is used to switch the control mode after determining that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition.

[0080] Specifically, when the grid-connected inverter of the wind turbine is in the grid-connected control mode, the receiving module 901 will perform pre-synchronization control of the voltage, amplitude and frequency at both ends of the grid-connected point after receiving the grid-connected control instruction, so that the voltage, frequency and phase at both ends of the grid-connected point can meet the grid-connected conditions.

[0081] When the grid-connected inverter is running, only one control mode will be in a normal state, and the other control mode cannot form a closed loop. When the grid-connected inverter is in the grid-building control mode, the orthogonal axis (hereinafter referred to as dq axis) current value output in the non-operating state is not equal to the dq axis current value in the operating state of the current grid-building control mode, which is bound to lead to a sudden change in the instantaneous current during switching, causing a grid-connected shock. The control module 902 performs pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine group to reduce the sudden change in the dq axis current value, so as to achieve a smooth transition when the grid-building control mode is switched to the grid-following control mode.

[0082] The switching module 903 determines whether the current value of the d-axis and the feedback current value of the d-axis meet the first switching trigger condition, and determines whether the current value of the q-axis and the feedback current value of the q-axis meet the second switching trigger condition. If the current value of the d-axis and the feedback current value of the d-axis meet the first switching trigger condition, and the current value of the q-axis and the feedback current value of the q-axis meet the second switching trigger condition, then the control mode is switched, that is, the grid-connected inverter of the wind turbine group is switched from the grid-building control mode to the grid-following control mode.

[0083] The wind turbine generator set structure / grid-following control mode switching device provided in an embodiment of the present invention receives a grid-connected control instruction and performs pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; performs pre-synchronization control of the direct-axis and quadrature-axis currents of the grid-connected inverter of the wind turbine generator set; if it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition, then the control mode is switched to achieve smooth switching of the control mode, thereby ensuring the stable operation of the wind turbine generator set.

[0084] Fig.10 is a schematic diagram of the structure of a wind turbine generator set configuration / grid-following control mode switching device provided by the tenth embodiment of the present invention, such as Fig.10 As shown, based on the above embodiments, the control module 902 further includes a first adjustment unit 9021 and a second adjustment unit 9022, wherein:

[0085] The first adjustment unit 9021 is used to perform a first-level proportional-integral adjustment based on a first difference between the current value of the direct axis and the feedback current value of the direct axis to generate an active reference; perform a first-level proportional-integral adjustment based on a second difference between the current value of the quadrature axis and the feedback current value of the quadrature axis to generate a reactive reference; the second adjustment unit 9022 is used to perform a second-level proportional-integral adjustment based on a third difference between the active reference and the active voltage to update the feedback current value of the direct axis; perform a second-level proportional-integral adjustment based on a fourth difference between the reactive reference and the reactive voltage to update the feedback current value of the quadrature axis.

[0086] Fig.11 1 is a schematic diagram of the structure of a wind turbine generator set configuration / grid-following control mode switching device provided in the eleventh embodiment of the present invention, such as Fig.11 As shown, on the basis of the above embodiments, further, the wind turbine generator set configuration / grid-following control mode switching device provided by the embodiment of the present invention further includes a judgment module 904, wherein:

[0087] The judgment module 904 is used to continue to perform pre-synchronization control of the direct-axis current of the grid-connected inverter of the wind turbine group if it is determined that the direct-axis current value and the direct-axis feedback current value do not meet the first switching trigger condition or the quadrature-axis current value and the quadrature-axis feedback current value do not meet the second switching trigger condition.

[0088] On the basis of the above embodiments, further, the first switching trigger condition includes that an absolute value of a first difference between the current value of the direct axis and the feedback current value of the direct axis is less than or equal to a first threshold;

[0089] The second switching triggering condition includes that an absolute value of a second difference between the quadrature-axis current value and the quadrature-axis feedback current value is less than or equal to a second threshold.

[0090] The embodiments of the apparatus provided in the embodiments of the present invention can be specifically used to execute the processing flow of the above-mentioned method embodiments, and its functions are not described in detail here, and reference can be made to the detailed description of the above-mentioned method embodiments.

[0091] Fig.12 is a schematic diagram of the physical structure of a computer device provided by the twelfth embodiment of the present invention, such as Fig.12 As shown, the computer device may include: a processor 1201, a communication interface 1202, a memory 1203 and a communication bus 1204, wherein the processor 1201, the communication interface 1202 and the memory 1203 communicate with each other through the communication bus 1204. The processor 1201 may call the logic instructions in the memory 1203 to execute the following method: receiving a grid-connected control instruction, and performing pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine is in a grid-connected control mode; performing pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine; if it is determined that the direct axis current value and the direct axis feedback current value meet the first switching trigger condition and the quadrature axis current value and the quadrature axis feedback current value meet the second switching trigger condition, then switching the control mode.

[0092] In addition, the logic instructions in the above-mentioned memory 1203 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0093] The present embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the methods provided by the above-mentioned method embodiments, for example, including: receiving a grid-connected control instruction, and performing pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine group is in a grid-connected control mode; pre-synchronization control of the direct-axis current of the grid-connected inverter of the wind turbine group is performed; if it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition, then the control mode is switched.

[0094] The present embodiment provides a computer-readable storage medium, which stores a computer program / instruction, and the computer program / instruction enables the computer to execute the methods provided by the above-mentioned method embodiments, for example, including: receiving a grid-connected control instruction, and performing pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine group is in a grid-connected control mode; performing pre-synchronization control of the direct-axis current of the grid-connected inverter of the wind turbine group; if it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition, then switching the control mode.

[0095] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0096] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0099] In the description of this specification, the description with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0100] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for switching between a wind turbine generator system's control mode and a grid-following control mode, characterized in that: include: Receive a grid-connected control instruction, and perform pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine generator set is in a grid-connected control mode; Performing pre-synchronization control of the orthogonal axis current on the grid-connected inverter of the wind turbine generator set; If it is determined that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition, the control mode is switched.

2. The method according to claim 1, characterized in that The pre-synchronization control of the orthogonal axis current of the grid-forming inverter of the wind turbine generator set comprises: A first-level proportional-integral adjustment is performed based on a first difference between the current value of the direct axis and the feedback current value of the direct axis to generate an active reference; a first-level proportional-integral adjustment is performed based on a second difference between the current value of the quadrature axis and the feedback current value of the quadrature axis to generate a reactive reference; A second-level proportional-integral adjustment is performed based on the third difference between the active reference and the active voltage to update the feedback current value of the direct axis; a second-level proportional-integral adjustment is performed based on the fourth difference between the reactive reference and the reactive voltage to update the feedback current value of the quadrature axis.

3. The method according to claim 1, characterized in that Also includes: If it is determined that the direct-axis current value and the direct-axis feedback current value do not satisfy the first switching trigger condition or the quadrature-axis current value and the quadrature-axis feedback current value do not satisfy the second switching trigger condition, the pre-synchronization control of the direct-axis and quadrature-axis currents of the grid-connected inverter of the wind turbine group continues.

4. The method according to any one of claims 1 to 3, characterized in that: The first switching trigger condition includes that an absolute value of a first difference between the current value of the direct axis and the feedback current value of the direct axis is less than or equal to a first threshold; The second switching triggering condition includes that an absolute value of a second difference between the quadrature-axis current value and the quadrature-axis feedback current value is less than or equal to a second threshold.

5. A device for switching the control mode of wind turbine generator system from one to another, characterized in that: include: A receiving module, used for receiving a grid-connected control instruction and performing pre-synchronization control of the voltage, frequency and phase at both ends of the grid-connected point; wherein, before receiving the grid-connected control instruction, the grid-connected inverter of the wind turbine generator set is in a grid-connected control mode; A control module, used for performing pre-synchronization control of the orthogonal axis current of the grid-connected inverter of the wind turbine generator set; The switching module is used to switch the control mode after determining that the direct-axis current value and the direct-axis feedback current value meet the first switching trigger condition and the quadrature-axis current value and the quadrature-axis feedback current value meet the second switching trigger condition.

6. The device according to claim 5, characterized in that The control module comprises: A first regulating unit is used to perform a first-level proportional-integral regulation based on a first difference between the current value of the direct axis and the feedback current value of the direct axis to generate an active reference; and to perform a first-level proportional-integral regulation based on a second difference between the current value of the quadrature axis and the feedback current value of the quadrature axis to generate a reactive reference; The second adjustment unit is used to perform a second-level proportional-integral adjustment based on the third difference between the active reference amount and the active voltage, and update the feedback current value of the direct axis; and perform a second-level proportional-integral adjustment according to the fourth difference between the reactive reference amount and the reactive voltage, and update the feedback current value of the quadrature axis.

7. The device according to claim 5, characterized in that Also includes: A judgment module is used to continue to perform pre-synchronization control of the direct-axis current and the quadrature-axis current of the grid-connected inverter of the wind turbine group if it is determined that the direct-axis current value and the direct-axis feedback current value do not meet the first switching trigger condition or the quadrature-axis current value and the quadrature-axis feedback current value do not meet the second switching trigger condition.

8. The device according to any one of claims 5 to 7, characterized in that The first switching trigger condition includes that an absolute value of a first difference between the current value of the direct axis and the feedback current value of the direct axis is less than or equal to a first threshold; The second switching triggering condition includes that an absolute value of a second difference between the quadrature-axis current value and the quadrature-axis feedback current value is less than or equal to a second threshold.

9. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 4.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program / instruction, which implements the steps of the method according to any one of claims 1 to 4 when executed by a processor.

11. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

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